Final answer:
Monkeys have tails, while apes do not. Apes are generally larger, more intelligent, and have larger brains relative to body size compared to monkeys.
Step-by-step explanation:
The main difference between monkeys and apes is the presence of a tail. Monkeys have tails, whereas apes, including humans, do not have tails. Monkeys are also more similar to other mammals than apes and humans are. Additionally, apes are generally larger than monkeys, have larger brains relative to their body size, and are more intelligent.